"Initializing" when reloading puzzle whose ID no longer exists after reload

[HactarCE]

steps to repro:

1. make a puzzle in HPS
2. load it
3. delete the HPS definition
4. reload the puzzle view using F5

expected behavior: error message saying "puzzle with ID does not exist"

actual behavior: stuck loading saying "initializing"

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also, we should generally handle panics better